Hi okedonk,
There are two options that can help you control this, the first option requires you to add a unique class to all the images that you would like to be shareable by Slingpic. For example, by adding the class ‘show-slingpic’ to all the images you want to be shared, you can then add this class in the options screen next to “show”.
Your other option is to use the “don’t show” option this works in the same way except that every image you add this class to Slingpic will not show.
If you are changing slingpic options manually, and not in the wordpress plugin settings page you can get more information here
Ben
